Sleep sack



FIG. 1 is a front perspective view of a sleep sack showing my newdesign;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is the top plan view thereof; and,

FIG. 7 is the bottom plan view thereof.

All of the broken lines illustrate portions of the sleep sack that formno part of the claimed design.

CLAIM The ornamental design for a sleep sack, as shown and described.